FC systems using two power supply sources—a fuel cell (hereinafter called an “FC”) and a secondary battery—and FC vehicles equipped with such FC systems have been known heretofore. In particular, if a secondary battery is installed for the purpose of power regeneration, that purpose can be fully achieved by a secondary battery having a small capacity relative to the FC.
However, in such FC systems having two power supply sources, if a failure occurs in any of the system components, such as an FC, a secondary battery, a drive motor that receives power supply from the FC and/or the secondary battery, and an inverter that controls the drive motor, and if some system components are unable to provide outputs, this results in an imbalance in outputs.
For example, in the case where an FC supplies an output of 100 kW to a 100 kW drive motor, if a failure occurs in the drive motor for some reason, a 100 kW output from the FC will flow into a secondary battery which is provided for regeneration.
In a system that adopts the configuration where a fuse is blown out if the entire output from the FC flows into the secondary battery due to the failure of the drive motor, in other words, in a system that adopts the configuration where individual system components constituting the FC system independently detect failures and stop for the self-protection, a failure in one system component may cause a failure in another system component, that is, there is the risk of so-called concurrent failures.
As a measure for such concurrent failures, for example, Patent Document 1 discloses a technique in which, if an overcurrent occurs in an FC step-up converter disposed between an FC and a load, the input voltage of a drive inverter disposed between the load and the step-up converter is restricted to be equal to or lower than a predetermined overvoltage threshold, so that any concurrent failures of the drive inverter, etc., can be suppressed even if an open-circuit failure occurs in a switching device of the step-up converter.